I am glad that with Yuneec you can grab the firmware updates straight from the ST16S and have the option to perform a segmented upgrade.Sorry to say but this is where Yuneec is stepping in their cranks. There is absolutely no reason they cannot verify the efficacy of their firmware prior to a release and publish download notes to minimize user errors in updating.
With dji products since P4, this is no longer possible (on the P3 line you could download the firmware update from their site but it had to flash all-at-once) and I had (still do) many failed updates performed both with dji Go4 and Assistant 2 on the PC; the latest saga was with the latest Mavic Air .540 update which took many tries to install.
And I do not forget the dreaded .400 upgrade which rendered the machine unsafe to fly, plus that you cannot downgrade with dji drones.
I agree however with your statement, I would also like to download the update files from their site, too.
But I also like that the situation is not so bad like dji and that I can always downgrade/segment flash whatever I want.